Mole Rats Get Stressed When Earth's Magnetic Field Vanishes, Study SuggestsNEWS | 23 October 2026The amazing animal known as Ansell's mole rat (Fukomys anselli) is one of evolution's most interesting offerings: half fuzzy sausage and half Nemesis from Resident Evil.
This social, chonky creature 'sees' magnetic fields with its near-blind eyes to navigate its hand-dug, kilometers-long subterranean tunnels; the longest built by any mammal, save ourselves.
Now, unique new research shows that this mole rat is so magnetically attuned that it shows signs of stress when Earth's guiding magnetic field nearly disappears – as any disaster movie connoisseur can understand.
The animal's amazing magnetosensation is still poorly understood, so a team led by neurobiologists from the Max Planck Institute for Neurobiology of Behavior used a new method to map the mole rats' brains to see how their neurons responded to magnetic field fluctuations.
Ansell's mole rat appears to sense magnetic fields with its near-blind eyes. (Headster/Wikimedia/CC BY 4.0)
"We show here, to our knowledge, for the first time, that a mammal shows an active avoidance reaction to the absence of a magnetic field," the researchers explain in a preprint uploaded to bioRxiv.
Magnetic navigation has been mostly studied in migratory birds, which traverse large swathes of land and sea, but some mammals are also magnetically inclined.
Intriguingly, even dogs and some primates have a molecule in their eyes that, in birds, seems to react to magnetic fields when stimulated by light, according to past Max Planck research.
But studies on magnetosensory brain areas in mammals have been limited to a single species, the subterranean Ansell's mole rat, the researchers note.
Oddly, previous research has found that numbing the surface of these animals' eyes with a local anesthetic robs them of their ability to build nests in their preferred compass direction, without robbing them of their limited ability to sense light.
So the researchers developed an imaging pipeline that used a chemical-based procedure to make the mole rats' brains transparent, creating a 3D map, or brain atlas.
To evaluate the accuracy of their atlas, they then injected a fluorescent tracer into the eyes of living mole rats to label the neural wiring and structural connections across the visual-brain pathway and overlay it onto their atlas.
The team's 3D mole rat brain atlas, and the eye-tracing experiment used to check its accuracy. (Zhang et al., bioRxiv, 2026)
Experimentally, they subjected mole rats to a changing magnetic field (CMF) and a near-zero hypomagnetic field (HMF), the latter of which was around 2 percent of the intensity of Earth's magnetic field in Germany, where the tests were conducted.
Every 30 seconds, the CMF changed either only in orientation or in both orientation and intensity, ranging from 20 to 70 times the strength of the near-zero field.
Surprisingly, the most robust and widespread brain response occurred in the presence of the HMF – in other words, a lack of stimulus proved the most salient stimulus.
The first magnetic field experiment. (Zhang et al., bioRxiv, 2026)
The mole rats exposed to the HMF displayed higher brain activity in regions linked to stress, anxiety, and fear, including the almond-shaped amygdala, which is also associated with decision-making and emotional processing.
Therefore, even though the near-absence of a magnetic field was expected to result in a neutral state, perhaps akin to a human perplexedly staring at a roadmap, it instead triggered brain activity resembling a stress response.
"Based on the neural activation patterns indicative of a stress-like state induced by HMF exposure, we hypothesized that mole rats perceive the lack of a magnetic field as aversive and consequently exhibit active avoidance behavior to HMF," the researchers write.
The same results manifested in a second experiment.
Mole rats were placed in a linear track wherein the researchers created a local magnetic-field anomaly by varying the magnetic intensity based on the animal's position. They spent significantly less time near an object placed inside the near-zero zone. Doubling the field strength had no such effect.
The second magnetic field experiment. (Zhang et al., bioRxiv, 2026)
But how mole rats sense magnetic fields is still an open question.
In fact, it may be more open than ever, as a recently published paper in the journal iScience reports no evidence for the naturally magnetic magnetite-based receptors thought to exist in mole-rat eyes, like little lodestones.
Further muddying the matter, this research links the mole rats' magnetic intuitions to a wide distribution of brain regions and circuitry, rather than a simple 'fridge magnet' neural center.
The intricate brain circuitry explored – including some missing puzzle pieces that depend on future study. (Zhang et al., bioRxiv, 2026)
Yet this study's novel imaging pipeline could provide a framework for future magnetosensation studies in mole rats and other animals – perhaps very, very many animals.
It also importantly reveals that near-zero magnetic fields may no longer provide useful controls in such studies, especially with mole rats, as they may stress the animals being tested.
"In summary, we present evidence that mole rats perceive the absence of the Earth's magnetic field," the researchers write.
"We show that the removal of this normally constant environmental stimulus, the Earth's magnetic field, activates stress-related brain circuits and triggers active avoidance behavior."
Had evolution taken a different twist, might the previously mentioned magnetic receptor remnants in primate eyes have bloomed and allowed people to (just as begrudgingly) find their way to work every morning along our planet's magnetic field? Who knows.
"Our findings demonstrate that the Earth's magnetic field constitutes a biologically significant sensory stimulus in mammals," the team concludes.
The study has not yet been peer-reviewed, but a preprint is available on bioRxiv.Author: Ivan Farkas. Source
